I've owned a 25-06 barrel and am now on a 25-06A.I barrel. I can't complain about its preformance. I use it mostly for varmints and varmint matches, target practice, although I have shot close range deer with it.
From my perspective, I probably wouldn't shoot a deer past 600 yards with it. So I would call it a mid range deer gun.
Long range varmints I have shot past 700 yards, and with the right bullets and scope you can kill them past 1200 yards.
Supposedly Berger is making some 125 VLD bullets later this year for the .257 caliber, I'm waiting on the edge of my seat.
I am building a 6mm Dasher, just because the long range bullet selection will be better varmints. I can fully dedicate my 25-06 IMP to a big game rifle.
Overall, the 25-06 has a better selection of big game bullets than the 6mm caliber.